The present invention relates to an ultraviolet irradiating device in which plural head portions which is used to cure ultraviolet curable resin used to adhere a small article part and a controller section are connected by an electric cable.
The ultraviolet curable resin is widely used from the fields of formation and printing of a resist film to the field of adhesive fixation of the small article part in an assembly process of an optical pickup, etc. The ultraviolet curable resin is generally designed so as to be cured by irradiating a near-ultraviolet ray near 365 nm in wavelength. However, a phenomenon (so-called oxygen obstruction) for obstructing a curing reaction of the resin by binding an oxygen molecule to a resin molecule is generated near the surface of the resin coming in contact with the air. Therefore, an ultraviolet ray (of a short wavelength) having large energy for overcoming this generation is required. Namely, it is known that the surface and inside of the resin are uniformly cured if the ultraviolet ray of a short wavelength (e.g., about 254 nm) for separating the oxygen molecule and the resin molecule from each other is irradiated together with the near-ultraviolet ray of about 365 nm in wavelength.
A mercury xenon lamp is generally used in a light source in the ultraviolet irradiating device used to cure the ultraviolet curable resin. The wavelength of the ultraviolet ray emitted from the mercury xenon lamp lies in a wide area of 200 to 600 nm. Accordingly, its short wavelength component contributes to the curing near the surface of the resin so that a comparatively uniform cured state is obtained.
Further, even when the ultraviolet irradiating device using the mercury xenon lamp is used, the ultraviolet ray is irradiated to the resin within the atmosphere of nitrogen as an inactive gas to promote the curing of the resin by restraining a bad influence of the oxygen molecule particularly near the surface of the resin. Namely, for example, a method for irradiating the ultraviolet ray to the ultraviolet curable resin within a chamber filled with nitrogen gas is executed as described in patent literature 1.
The ultraviolet irradiating device described in the patent literature 1 is large-sized production equipment used in the fields of formation and printing of the resist film. A compacter structure is used in the ultraviolet irradiating device used to adhere the small article part (e.g., plastic lens) in the assembly process of an optical pickup, etc. For example, a structure obtained by connecting a device main body building-in a light source using the mercury xenon lamp and a compact head portion by an optical fiber cable is used. The ultraviolet ray emitted from the mercury xenon lamp is guided to the head portion through the optical fiber cable, and is irradiated to an adhering portion coated with resin from the head portion.
Further, for example, when the outer circumferential portion of the plastic lens is fixed to its holder, it is necessary to coat plural contacting portions (e.g., three to four portions) of the outer circumferential portion of the plastic lens and the holder with the ultraviolet curable resin, and simultaneously fix the plural contacting portions. Namely, it is necessary to simultaneously cure the resin of the plural contacting portions. This is because the accuracy of a fixing position of the plastic lens gets worse when the resin is sequentially cured every one portion.
Therefore, the above ultraviolet irradiating device for adhering the small article part has plural heads and has a structure in which the device main body and the plural head portions are respectively connected by plural optical fiber cables. One mercury xenon lamp is built in the device main body, and the ultraviolet irradiating device is constructed such that the ultraviolet ray emitted from the mercury xenon lamp is simultaneously incident to the plural optical fiber cables. The ultraviolet rays propagated within the respective optical fiber cables are simultaneously irradiated to the exterior from the head portions connected to the tips of the respective optical fiber cables.
[Patent literature 1] JP-A-5-305259
Since a heat ray is also included in the ultraviolet ray emitted from the above mercury xenon lamp, the heat ray is shielded by using a filter. However, for example, in a use for adhering and fixing a precise optical part such as a micro-plastic lens, there are fears that heat included in the irradiated ultraviolet ray badly affects the fixation accuracy of the part and the precise part is distorted by the heat.
Further, a member obtained by coating a quartz optical fiber with a flexible cable of stainless steel is used in the optical fiber cable for guiding the ultraviolet ray emitted from the mercury xenon lamp to the head portion. However, this optical fiber cable is expensive and attenuation of the ultraviolet ray is large. Therefore, a problem exists in that no ultraviolet ray can be guided until a far place.
Further, as mentioned above, the structure for propagating the ultraviolet ray emitted from one mercury xenon lamp in the plural optical fiber cables and irradiating the ultraviolet ray from the plural heads is used. Therefore, the intensity (light amount) of the ultraviolet ray irradiated from each head and on-off timing of the irradiation cannot be individually controlled.
In recent years, a light emitting diode (LED) of high output is practically used as the light source of the ultraviolet ray instead of a high pressure mercury lamp and the mercury xenon lamp. If this light emitting diode is built in the head portion as the light source, the above problems can be solved at a stroke.